The Mechanical and Material Assessment Core focuses on providing complementary techniques for determining mechanical properties and performing material characterization of native and engineered orthopaedic tissues, as well as providing in vivo models to study adaptation of these skeletal tissues to mechanical stimuli. Skeletal tissues include bone, cartilage, ligament, menicus and tendon, and accomplish their in vivo function through a wide range of material compositions and mechanical behavior. These tissues are responsive to their biophysical and biochemical environments, adapting their composition and structure. Skeletal function is dictated by the properties of the materials and the spatial distribution of the materials within the structure. Assessing function is fundamental to endeavors aimed at musculoskeletal repair and regeneration, because these attempts will only succeed if mechanical function can be restored. Therefore, the goals of the Mechanical and Material Assessment Core are to provide equipment and methodologies for mechanical testing and material characterization of musculoskeletal tissues and organs;to train investigators in the use and interpretation of these techniques;and, to develop new applications and methodologies to support the research programs of investigators within the Core Center's biomedical research base. New testing methodologies suitable to the biological approaches being used in current and planned experiments by cOre investigators have been developed, particularly for in vivo small animal experiments, to complement techniques (such as micro-CT, histology, and Fourier transform infrared imaging) available in the Center's other research cores. These efforts are periodically reviewed by user groups, which include biomedical engineers, clinicians, biologists, radiologists, chemists, and their students. The result has been an expansion of collaborations among the multidisciplinary biomedical research base and the introduction of new investigators to the capabilities of the core.